There are many simple words in the English language that are hard for foreign speakers to master.

That's because English words often have several different meanings and can be difficult to pronounce.

English is a notoriously difficult language to learn, from its inconsistent pronunciation to the endless list of irregular verbs.

For some people learning the language, it's extremely difficult to nail down relatively simple words that many native speakers take for granted.

Business Insider reached out to the online language-learning platform Duolingo to find out some of the most difficult words in English for non-native speakers to learn. The site collected data from speakers of Spanish, Portuguese, Russian, and Arabic and came up with 15 simple words that are especially tough.

Bench

Ceiling

Apartment

Mushroom

Toes

Isle

Shore

Addition

Net

Dish

Leaf

Its

Pineapple

Lounge

Harbor

For many of the words, it's the spelling and pronunciation that cause trouble for English learners, a spokeswoman for Duolingo told Business Insider. It isn't immediately clear how "isle" and "ceiling," for example, should sound.

In other cases, difficulty arises when a word is polysemous, or when it has multiple meanings. "Shore," "dish," "harbor," "net," and "lounge" all could mean various things depending on the context, and it can be difficult for English learners to suss out the correct context.

And then there's pineapple, a fruit which contains neither pine nor apple. Imagine teaching someone that word for the first time, and you can understand its inclusion on the list. It's just one of the many deceptively tricky words that comprise the colorful English language.